Today, networked devices, such as user terminals, machines, wireless sensors, etc., are assumed to be always on-line and to be always reachable.
This means that whenever a device wants to communicate or wants to be able to receive any data, such as messages, the device has to be connected to the network. Since most of the devices connected to mobile networks are normally powered by batteries, their energy efficiency requires that the duration of active communication is minimized. This is especially important for machine-type communication or wireless sensors, where the battery in some cases is supposed to last the full lifetime of the device. This means that a single battery may have to last several years.
In the design of legacy communication systems, it is well known to apply a DRX technique to reduce the time for active communication of devices. This is generally made by periodically switching off the receiver of the device, until again switching on the receiver and listening to a control channel, for instance the physical downlink control channel (PDCCH) in long-term evolution (LTE), to find out whether there is new data scheduled for the device, or not. DRX algorithms are also used in other communication standards of various different generations, such as global system for mobile communications, high-speed packet access, and worldwide interoperability for microwave access, to mention a few.
Current techniques are typically controlled by timers in a cyclic manner. Each cycle, also called DRX cycle, occurs with a periodicity of tens of milliseconds (ms). A DRX cycle typically comprises an on-duration period, and an inactivity period. Every listening period lasts a predefined period of time to find out whether any data is scheduled for the device. This period of time is the on-duration period and lasts typically a few milliseconds. If data is scheduled, the device will be kept active to wait for further data even though there is no more data scheduled for the device. This time period is the inactivity period, and lasts typically in the order of one hundred milliseconds. The setting of length of the time periods involves a trade-off between reducing battery power consumption and latency of any scheduled data. The absolute value of these time periods may be subject to changes in the future, but their relative ratio is assumed to be similar as today.
For DRX techniques employing timers, the timers are usually set to reasonably large values, such as the values given above, to provide enough time space for a scheduler to effectively schedule communication into time-frequency resource blocks.
This has the effect that the devices need to be in active mode throughout reasonably long listening windows even though no data is scheduled for them. This leads to unnecessary battery power consumption and shorter battery life.